ABSTRACT
Reliable and large-scale manufacturing routes for perforated graphene membranes in separation and filtration remain challenging. We introduce two manufacturing pathways for the fabrication of highly porous, perforated graphene membranes with sub-100-nm pores, suitable for ultrafiltration and as a two-dimensional (2D) scaffold for synthesizing ultrathin, gas-selective polymers. The two complementary processes-bottom up and top down-enable perforated graphene membranes with desired layer number and allow ultrafiltration applications with liquid permeances up to 5.55 × 10-8 m3 s-1 Pa-1 m-2. Moreover, thin-film polymers fabricated via vapor-liquid interfacial polymerization on these perforated graphene membranes constitute gas-selective polyimide graphene membranes as thin as 20 nm with superior permeances. The methods of controlled, simple, and reliable graphene perforation on wafer scale along with vapor-liquid polymerization allow the expansion of current 2D membrane technology to high-performance ultrafiltration and 2D material reinforced, gas-selective thin-film polymers.
ABSTRACT
In chemical separation, thin membranes exhibit high selectivity, but often require a support at the expense of permeance. Here, we report a pinhole-free polymeric layer synthesized within freestanding carbon nanotube buckypaper through vapor-liquid interfacial polymerization (VLIP). The VLIP process results in thin, smooth and uniform polyamide and imide films. The scaffold reinforces the nanofilm, defines the membrane thickness, and introduces an additional transport mechanism. Our membranes exhibit superior gas selectivity and osmotic semipermeability. Plasticization resistance and high permeance in hydrocarbon separation together with a considerable improvement in water-salt permselectivity highlight their potential as new membrane architecture for chemical separation.
ABSTRACT
A two-dimensional (2D) porous layer can make an ideal membrane for separation of chemical mixtures because its infinitesimal thickness promises ultimate permeation. Graphene--with great mechanical strength, chemical stability, and inherent impermeability--offers a unique 2D system with which to realize this membrane and study the mass transport, if perforated precisely. We report highly efficient mass transfer across physically perforated double-layer graphene, having up to a few million pores with narrowly distributed diameters between less than 10 nanometers and 1 micrometer. The measured transport rates are in agreement with predictions of 2D transport theories. Attributed to its atomic thicknesses, these porous graphene membranes show permeances of gas, liquid, and water vapor far in excess of those shown by finite-thickness membranes, highlighting the ultimate permeation these 2D membranes can provide.
